This is an application for a Mentored Clinical Scientists Development Award for E. Sander Connolly, Jr., MD. who is in the first year of his assistant professorship in neurological surgery. He will spend 80% of his time in a program of scientific training under the guidance of David Stern, M.D.(Mentor). This training will be driven by a project whose theme is to examine the role of the microvasculature in reperfused stroke, both in terms of leukocyte adhesion receptor expression, as well as, the activation of the endogenous coagulation and fibrinolytic systems. The first specific aim is based upon a murine model of focal cerebral ischemia and reperfusion, in which wild type mice and those deletionally mutant for an adhesion receptor gene (ICAM-1, or -2, P-selectin or CD18) or for a fibrinolytic protein (tPA, uPA, or PAI-1) will be examined to determine whether microvascular thrombosis and leukostasis are operant in stroke, and the mechanisms involved. The physiological importance of these findings will be determined by measurements of fibrin, platelet, and leukocyte accumulation, relative cerebral blood flow, cerebral infarct volumes, intracerebral hemorrhage, neurological deficit and mortality. The second specific aim is based upon a primate (baboon) model of reperfused stroked, which employs a well characterized bilateral ACA, and ipsilateral ICA temporary (1h) occlusion. Leukocyte adhesion and microvascular thrombosis will be studied with particular reference to important mechanisms in the murine model. Correlation will be performed using graded neurological examinations, transcranial doppler blood flow measurements, cerebral imaging (MRI with FLAIR and diffusion/perfusion sequences), and postmortem tissue examination. SPECT-scanning will be employed to image platelet and leukocyte influx. Guided by the results of aim #1 and aim #2 the PI plans to use either an anti-platelet strategy (GPIIb/GPIIIa antagonist) or an anti-adhesion receptor strategy (humanized anti P and E-selectin antibody) to demonstrate functional significance in primates. The pursuit of these Specific Aims will provide the critical focus during which time the PI will gain a training experience, learning new techniques as well as the methods of scientific inquiry under the immediate supervision of the Sponsor, a recognized expert in the field of vascular biology. In addition to daily interactions with the Sponsor and members of the immediate laboratory, the PI will participate in a formal series of lectures in vascular biology, given by the faculty as well prominent outside speakers. In addition, the Sponsor holds a series of Work-in- Progress seminars, in which members of the laboratory present intermediate data nad receive specific suggestions from other laboratory members and invited faculty. Finally, the PI will enroll in the Columbia University School of Public Health, in order to take course in biostatistics and experimental research design, to round out the didactic portion of the proposed training. These intellectual resources, combined with the fiscal resources to support the project which will be provided by the Chain of Neurological Surgery, will enable the PI to develop into an independent investigator by the conclusion of the training period.